Association Between S-1 Treatment Duration and Disease Control in Advanced Non-small-cell Lung Cancer.

Background/Aim: S-1 monotherapy is used for a subset of patients with advanced non-small-cell lung cancer (NSCLC); however, predictors of prolonged treatment and survival remain unclear. The aim of this study was to investigate clinical factors associated with extended S-1 treatment and clinical outcomes in patients with advanced NSCLC. Patients and Methods: We retrospectively reviewed the data of 32 patients with stage IIIB/IV or recurrent NSCLC who received S-1 monotherapy at Kanazawa Medical University Hospital from January 2015 and December 2025. Patients were classified into a long-term treatment group (≥90 days, n=13) or a short-term treatment group (<90 days, n=19). Results: =0.003). Treatment-related adverse events were mild: no grade ≥3 toxicities or treatment-related deaths were observed. Conclusion: Prolonged S-1 treatment was associated with improved disease control and longer overall survival in patients with advanced NSCLC. These findings suggest that disease stabilization, rather than tumor shrinkage, may be a key determinant of the long-term benefit of S-1 monotherapy.